Integrated circuits such as computer chips are manufactured from semiconductor wafers. These wafers are subjected to numerous steps during the process of making integrated circuits. This generally entails transporting a plurality of wafers from one place to another for processing. As part of the processing procedure, wafers may be temporarily stored or shipped in containers to other plants or to end users. Such intra-facility and extra-facility movements may generate or expose the wafers to potential wafer ruining contaminants and to physical shocks. In order to reduce the deleterious effect of such conditions on the wafers, specialized containers have been developed to minimize the generation of contaminants and to isolate wafers from physical shock.
Plastic containers have been used for decades for transporting and storing wafers in-between process steps. Such containers have highly controlled tolerances for interfacing with processing equipment as well as the equipment/robots that transport the containers. Moreover, it is desirable in such plastic containers to use components that are attachable and removable without using metallic fasteners such as screws, since metal fasteners can cause particle generation when inserted and removed.
Additional, required or desirable characteristics of containers to transport and/or store semiconductor wafers include light weight, rigidity, cleanliness, limited gaseous emissions, and cost effective manufacturability. The containers provide hermetic or close to hermetic isolation of wafers when the containers are closed. Simply stated, such containers need to keep the wafers clean, uncontaminated, and undamaged. Additionally, carriers need to maintain their capabilities under the rigors of robotic handling which includes lifting the carrier by the robotic flange positioned at the top of the container.
Front opening wafer containers have become the industry standard for transporting and storing large diameter 300 mm wafers. In such, containers the front door is latchable within a door frame of a container portion, and closes a front access opening through which the wafers are robotically inserted and removed. When the container is fully loaded with wafers the door is inserted into the door frame of the container portion and latched thereto. When seated, cushions on the door provide upward, downward, and inward constraint for the wafers.
The semiconductor industry is now moving toward using even larger, 450 mm diameter, wafers. The larger diameter wafers, although providing cost efficiencies, also provide increased fragility, greater weight, and present issues associated with handling and storing the larger wafers in containers made of plastic. Deflection and related problems associated with the expanses of plastic on the top, bottom, sides, front, and back are exacerbated, as are door sealing issues due to uneven seals and distortion of the door to door-frame interface due to the deflection of container surfaces.
A particular problem arises with physical shocks to which wafer containers may be subjected when shipped between facilities, especially when the containers are shipped individually. Wafer containers, especially those for larger size wafers such as 300 mm and 450 mm wafers, are typically designed such that the wafers are supported and cushioned on shelves with the plane of each wafer being generally horizontal. When shipped individually, however, a wafer container may be inverted or placed in a position where the wafers are not horizontal. In addition, the container may be subject to considerable shock loads when being handled. Such loads can exceed 8 G and may reach 20 G or more, which can fracture wafers that are not properly supported and restrained.
Previous attempts at addressing the problem of fractured wafers in transit of wafer containers have involved providing additional external cushioning members and packaging on the outside of sealed wafer containers. These prior attempts have met with limited success, and have not fully addressed the problem of wafer damage when containers are transported.
What is needed in the industry is a wafer container that provides greater physical shock resistance and better wafer support under typical shipping conditions.